Plastic and other film produce bags are commonly used in supermarkets, grocery stores and other markets where sanitation and ease of use in limited spaces are important factors. These bags have advantages in that they are relatively inexpensive to produce, provide substantial carrying capacity and may include easy opening features. Most bags are produced with a heat welded bottom seam. Many bags have side or bottom gussets to provide for increased carrying capacity or to provide convenient carrying handles in “T-shirt” style gusseted bags. In both gusseted and ungusseted bags, the weakest point is usually at the bottom bag seal. For gusseted bags the weakest point is typically at the point where the bottom seal of the gussets joins the bottom seal for the ungusseted portion of the bag. The present invention provides for a substantially stronger bottom seal for both gusseted and ungusseted bags. In addition, the same technology is used to provide T-shirt style bags with substantially stronger handles.
U.S. Pat. No. 4,931,034, issued to Wagner is directed to bags made from thermoplastic synthetic resin sheeting having cutoff weld seams and process for producing the bags. The bags have a bottom and/or lateral seam fashioned as a cutoff weld seam which are severed by transverse cutoff weld seams from tubular film sheets optionally provided with lateral creases. The bottom seam is designed to be reinforced in the form of a cutoff weld seam and to allow the bags to be readily set in an upright position since there is no interfering protrusion in the seam zone on the outside. The shopping bags may be produced from a tubular sheet with lateral pleats transported in succession into the welding stations. In the first welding station, the flush seam is welded with a certain width in the zone of the subsequent bottom cutout seam over the entire breadth of the tubular sheet. Utilizing the technique of a welding blade, the application of heat is effected unilaterally and the welded material is severed into two parts and simultaneously weld seams are created on both sides of the parting line. While the welding bar produces the flush seam, the wire or the hot strip merely affects a cutting step thus allowing for two flush seams to be produced simultaneously and severed by means of a hot wire. Thus, the invention is able to produce bags with an improved strength and tear resistance of the bottom seams of the plastic bags.
U.S. Pat. No. 3,618,478, issued to Piazze, discloses a three dimensional bag with reinforced bottom and method of forming the same. This patent describes the formation of flexible bags from heat sealable plastic film in order to provide a square or rectangular bottom structure that is thus “reinforced” and thus provides a stronger bag. The heat sealable plastic film material utilizes supplementary seals in the gusseted bottom structure which strengthens the bottom end areas in order to prevent rupturing when the bag is filled with a flowable product. The ends of the gusset bottom folds are sealed to the sidewalls by extensions of the side seals such that the inner fold line and side seal lines are joined together with the outer gusset folds in order to provide the additional strength. The bag is formed from two rectangular wall forming panels which are flattened upon one another and connected along the side edges by bead-like seals or welds. The bag bottom is formed with a folded edge connecting the two wall panels wherein the fold is a bellows-type or an infolded gusset to provide a bottom structure consisting of two panels on the opposite sides of a centerfold. The meeting points are at the juncture of the gusset inner fold and the side seals which provides triangular areas at the base of the vertical side thus providing multiple thicknesses of material and the increased strength.
U.S. Patent Application No. 2010/0022375 published for Colla is directed to a method for the production of packaging bags having a reinforced base region and a device for carrying out the method. It is thus proposed to have a folded and bonded base reinforcement providing a high loading capacity with the folded portion providing the extra layers that are thus held by an adhesive to make the bag stronger. A pair of rollers is used to draw the continuous film web toward the cutting unit wherein the web has a portion forming the folding portion that protrudes beyond a retaining device. When the film web reaches its end position, the film is severed in the cutting unit and subsequently adhesive is provided by a plurality of nozzles and ultimately a bond is formed with the folding portion. After the hot glue is applied, the folding portion which protrudes beyond the retaining unit is folded over and upward along a folding line and pressed from above onto the film by means of a folding device.
U.S. Pat. No. 3,622,421, issued to Cook is directed to a method for forming bags from thermoplastic tubing particularly concerned with a method for forming bags by transversely perforating and sealing a flattened tube of thermoplastic film material thus dividing the web into connected series of bags. The web is passed through a perforating unit which applies lines of transverse perforations at intervals corresponding to the length of the finished bag. The web then passes through a pair of draw rolls and ultimately around a drum with spaced vacuum ports only enabling a seal to be formed. The web then passes beneath a sealing bar with heating elements such that a transverse seal is formed. After cooling, the web passes through a perforating mechanism that defines one bag from the succeeding bag and ultimately the web is wound onto a reel.
U.S. Pat. No. 3,850,724 issued to Lehmacher is directed to an apparatus and method for fabrication of carrying bags including reinforced double walled plastic carrying bags. The high carrying strength bags are formed utilizing a side-folded and seam bottom welded thermoplastic film bag structure with a double wall comprised of two thermoplastic films. The main body portion of a length of thermoplastic flattened tube longitudinally is infolded at opposite vertical margins to form a pair of infold panels. Handles or grip elements which are formed of thermoplastic film material are attached to and extend above the bag mouth outer margin utilizing a tape strip. The method provides for formation of a flat and well defined rectangular bottom bags with wall panel reinforcement. The front and rear wall panels of the body of the bag are comprised of inner and outer layers with a reinforcing insert disposed therebetween. Each insert runs across the entire bag to the infold edges from a location downwardly from the bag mouth edge. Grip elements are secured by an adhesive tape strip thus providing reinforcement for the handle portions.
While other variations exist, the above-described designs for reinforced bags are typical of those encountered in the prior art. It is an objective of the present invention to provide merchandise and produce bags with substantially stronger bottom seams. It is a further objective to provide T-shirt style bags that lack the typical points of weakness adjacent the joint of the bag gusset seams with the bag bottom seam. It is yet a further objective to provide T-shirt style bags with substantially stronger handles. It is a still further objective of the invention to provide bags with stronger seams that use a minimal amount of additional film material to provide the additional strength. Finally, it is an objective of the invention to provide methods and apparatus for production of such high strength bags that are simple and economical to use.
While some of the objectives of the present invention are disclosed in the prior art, none of the inventions found include all of the requirements identified.